Conventionally, when semiconductors are to be enclosed with resin by molding, lead frames carrying semiconductor chips are set in place between the parting line surfaces or fitting surfaces of the upper and lower molds, and the molds are thereafter clamped together. A preheated resin material, such as epoxy resin or like thermosetting synthetic resin is fed to a single large pot in the center of one of the molds and plasticized in the pot by being subjected to pressure with a plunger. The plasticized material is pressingly injected into the cavities through the main runners, auxiliary runners and gates, and is molded with semiconductor chips enclosed with portions of the material.
In such molding apparatus, the distances between the pot and the cavities are long and different from each other. With the passage of time, therefore, thermosetting of the resin is inevitably accelerated with different thermosetting degrees in the resin flow course. It is therefore difficult to obtain molded articles of a constant quality with a good molding efficiency.
In order to eliminate such disadvantage, the pressure of injecting the resin from the pot may be increased to provide a higher resin flow speed. In such a case, however, the resin flow pressure into the cavities becomes too strong, thereby disadvantageously to break or deform fine metallic conductors or the like attached to the semiconductor chips.
Moreover, the main runners, auxiliary runners and gates are also charged with the resin material used. This entails a serious loss of resin material not used for molded articles, thus disadvantageously affording a reduced yield.
Since the resin material is thermosetting and is therefore not reusable, the waste of the material results in a great economical loss.
In order to eliminate the above-mentioned disadvantages, the inventor of the present invention has successfully proposed an apparatus for enclosing a pluraltiy of semiconductors with resin by molding at the same time with the use of molds having a plurality of cavities and pots, by injecting under pressure a resin material supplied to the pots, to the respective cavities only through the gates, or directly without passing the material through the main runners, auxiliary runners and gates.
In the molding apparatus above-mentioned, a movable lower mold opposed to a stationary upper mold has a plurality of pots into which plungers are fittingly inserted, and a resin material feed port is opened to the mold suface of the lower mold. When a resin material is to be fed into the pots with the hand, it is necessary to feed a resin material with the hand inserted between the opened upper and lower molds. Such feed operation may be attended with danger that the operator gets burnt in the hand with the hand touching the heated molds, or that the hand is caught in the molds in case the molds are unexpectedly clamped during the material feed operation.
In such molding apparatus, it is necessary to dispose a plunger lifting/lowering mechanism at the lower mold side, in addition to the lower mold lifting/covering mechanism. The construction becomes therefore very complicated at the lower mold side. Accordingly, assembling and disassembling of the entire molding apparatus become troublesome and difficult, resulting in difficult maintenance and checking of the parts.